[R] ggplot2 directional line type?

[Malcolm Ryan]

I'm doing a path plot with ggplot2, the result is looking very nice, but I want to give some indication of which direction the lines are going. I thought of using colour gradients, but it doesn't look right. What would be ideal is a line type that indicated direction, something like ">>>>>>>". Is there any way to achieve this? Or can anyone suggest another way of representing this information?

Malcolm